Pipeline & Underground Utility Construction

Water, sewer, gas and oil pipeline crews combine deep trenches, heavy pipe, existing live utilities and traffic, which makes for some of the highest-risk work in construction.

• Construction
• Utilities

Top hazards

• Trench cave-ins. See Trenching.
• Striking existing gas, electric and fiber lines
• Struck by or crushed by swinging pipe and side booms
• Hazardous atmospheres in trenches and manholes
• Pressure test failures (hydrotests and air tests)
• Radiation from industrial radiography of welds
• Traffic in street work

Key practices

• Call 811 and expose crossing utilities with hand digging or vacuum excavation. See Call 811.
• Use trench boxes or shoring, and stay inside them.
• Keep out from under pipe being lowered; use tag lines.
• Test the air in trenches near sewers, landfills and gas lines.
• Clear the area for pressure tests and use restrained fittings.
• Stay outside the radiography boundary (marked with signs and rope) during weld X-rays.

Manholes and vaults

Sewer manholes, valve vaults and utility vaults are often permit-required confined spaces. They can hold hydrogen sulfide, methane, low oxygen and carbon monoxide. Test the air before entry and continuously, ventilate, use a retrieval system and attendant, and never enter to rescue a coworker without proper equipment. See Confined Spaces.

Pipe handling

• Pipe can roll off stacks and trucks. Chock it and stack it on level ground.
• Side booms and excavators lowering pipe need trained operators, rated rigging and a signal person.
• Pipe layers in the trench must stay inside the trench box and out from under the pipe until it’s nearly in place.
• Big diameter pipe can trap workers between the pipe and the trench wall or box.

Pressure testing

A pipe or fitting that fails during a pressure test can release energy violently, especially with air or gas. Restrain fittings, clear the area, use the test method in the specifications, and never stand at the end of a pipe under test.

Working in streets

Street work adds traffic, pedestrians and nearby buildings. Set up traffic control, protect pedestrians with barriers, cover open trenches at the end of the day, and watch for basements and footings next to the trench. See Work Zones and Excavating Near Structures.

Daily checklist

• 811 ticket valid; crossings potholed
• Competent person inspected the trench
• Trench box or shoring in place; ladder within 25 feet
• Air tested in trenches near sewers and gas
• Traffic control and pedestrian protection set
• Pipe stacks chocked; lifting gear inspected

Last updated: October 1, 2026